1. Field of the Invention
The present invention relates to a printer apparatus and, more specifically, to a printer apparatus including a grid roller and a press roller for paper feeding.
2. Description of the Background Art
A printer apparatus including a grid roller and a press roller as a paper feeding mechanism has been known. This type of printer apparatus has a grid roller 104 and a press roller 108 pressing a sheet of paper onto grid roller 104 arranged as shown in FIG. 14. On a surface of grid roller 104, ceramic particles are applied to increase friction with the sheet of paper 110 fed thereto and to reliably feed the sheet of paper 110.
At the time of printing on paper 110, paper 110 is fed toward grid roller 104, while grid roller rotates, at first, in a direction opposite to the paper-feed direction. Accordingly, when a tip-end of paper 110 reaches a gap between grid roller 104 and press roller 108, the paper is not immediately fed through the gap, but first subjected to skew correction, by which positional deviation of paper 110 is corrected so that the front end of paper 110 is positioned parallel to the axis of rotation of grid roller 104, in case where paper 110 is fed askew.
After skew correction of paper 110, grid roller starts rotation in the opposite direction, and paper 110 is fed out from the gap between grid roller 104 and press roller 108, and printing is done on paper 110. In this type of printing apparatus, printing on the paper is done in the manner described above. Japanese Patent Laying-Open No. 2002-154702 proposes a paper feeding apparatus having the skew correction function.
Sheets of paper for printing may have front-end portion bent or warped (dog-eared). Particularly, envelopes tend to have corners bent, because they are gummed. The printer apparatus described above suffers from the following problem when printing is to be done on a sheet of paper having a tip end portion bent or warped.
First, assume that paper 110 fed toward grid roller 104 has its tip end portion bent (dog-eared) as shown in FIGS. 15 and 16. When the tip end of paper 110 as such comes close to the gap between grid roller 104 and press roller 108, it follows that the bent portion 110a of paper 110 comes to be in contact with the surface of grid roller 104 earlier than the portion that is not bent. At this time, grid roller 104 is rotating in a direction (arrow 122) opposite to the paper feed direction (arrow 121), and therefore, paper feed of the dog-eared side of paper 110 is hindered as compared with the side not having the bent corner.
Consequently, the paper (in solid line), of which skew supposed to be corrected as shown by the dotted line 125, is skewed. When grid roller 104 starts rotation in the direction of arrow 123 as shown in FIGS. 19 and 20 in this state, paper 110 comes to be fed much skewed from the originally intended state (dotted line 126). As a result, printing on the paper 110 is also skewed.